One Million Percent Tunnel Magnetoresistance in a Magnetic van der Waals Heterostructure

We report the observation of a very large negative magnetoresistance effect in a van der Waals tunnel junction incorporating a thin magnetic semiconductor, CrI₃, as the active layer. At constant voltage bias, current increases by nearly one million percent upon application of a 2 T field. The effect arises from a change between antiparallel to parallel alignment of spins across the different CrI₃ layers. Our results elucidate the nature of the magnetic state in ultrathin CrI₃ and present new opportunities for spintronics based on two-dimensional materials.